Wireless communication systems are widely used to provide voice and data services for multiple users using a variety of access terminals such as cellular telephones, laptop computers and various multimedia devices. Such communications systems can encompass local area networks, such as IEEE 801.11 networks, cellular telephone and/or mobile broadband networks. The communication system can use a one or more multiple access techniques, such as Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Code Division Multiple Access (CDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA) and others. Mobile broadband networks can conform to a number of system types or partnerships such as, General Packet Radio Service (GPRS), 3rd-Generation standards (3G), Worldwide Interoperability for Microwave Access (WiMAX), Universal Mobile Telecommunications System (UMTS), the 3rd Generation Partnership Project (3GPP), Evolution-Data Optimized EV-DO, or Long Term Evolution (LTE).
In a fully utilized OFDMA or multiple input, multiple output (MIMO) OFDMA wireless communications system without power control, base stations occupy the entire band with a nominal transmit power. Base stations may also be referred to as enhanced Node Bs (eNBs) controllers, base terminal stations, and the like. Such base stations transmit to and receive transmissions from user devices. User devices may also be referred to as user equipment (UE) mobile stations, terminals, access terminals, communications devices, and so forth.
In some systems, such as LTE, a base station generally does not have information about the short term fading information of the interference from other base stations, the channel resource utilization and precoder matrices used by other base stations. Therefore, the base station may not be aware of the interference spectrum received by the user devices it serves.
Some systems have addressed this issue by making a base station know the power spectrum masks from neighboring base stations. Here, a base station can better estimate the interference spectrum at each user device and perform a better scheduling and modulation and coding scheme (MCS) adaptation. One example of this is a system where fractional frequency reuse power control is applied and other base stations are aware of the base station power mask spectrum, for example, through backhauling or system planning Another example is a system where base stations are made aware of spectrum underutilization resulting from non-fully loaded base stations. Once a base station is aware of spectrum underutilization of its neighboring base stations, the base station can improve its scheduling, modulation, and coding scheme (MCS) adaptation. In both examples, the base station may be made aware of the underutilized power spectrum through pre-planned deployment power masks or through relative narrowband transmit power (RNTP) signaling between base stations.
In some systems, such as Long Term Evolution (LTE) systems, the base station gathers information about the downlink channel by polling receiving channel quality index information (CQI) from user devices on the network. In practical applications, however, the CQI reported by the user device may be higher or lower than the actual channel quality index. Because of this, an LTE base station adaptively adjusts the CQI reported by the user device by monitoring acknowledge (ACK) and non-acknowledge (NACK) signals from the user device. Such adaptation, however, takes time. During this adaptation time, the user device may be dropping packets because the base station is transmitting using an MCS level that is too high for the actual channel, or the user device may be operating at a slower data rate because the base station is transmitting using an MCS level that it too low for the actual channel. In either case, the performance of the user device is suboptimal during the adaptation time.